Prenatal ultrasound diagnosis and quality control of fetal nuchal translucency. / èƒŽå„¿é¢ˆé¡¹é€æ˜Žå±‚äº§å‰è¶ å£°è¯Šæ–­åŠè´¨é‡æŽ§åˆ¶.

OBJECTIVES: In clinical ultrasound examinations, it is challenging to perform quality control on the images of each fetal nuchal translucency (NT) and crown-rump length (CRL). However, small measurement differences can increase the probability of false-positive or false-negative diagnosis. Therefore, it is necessary to establish a quality control system for fetal NT examination. This study aims to control the quality of fetal NT and CRL measurements, evaluate the accuracy of ultrasound physicians in early pregnancy NT measurements, and analyze the impact of increased fetal structure screening on the detection rate of chromosomal abnormalities. METHODS: Data were collected from cases before and after 12 months of NT examination quality control, with 2 214 before quality control and 2 538 cases after quality control. Three quality control data metrics were analyzed: NT multiple of median (NT-MoM), standard deviation (SD) of log10MoM [(SD) log10MoM], and the slope of NT on CRL (SNC). The performance of NT measurements was monitored through the individual CRL NT-MoM within the 0.9-1.1 MoM range of the normal median curve, while grouped based on different years of experience (<3 years, 3-6 years, >6 years), and NT-MoM values among these groups were compared. Data on NT thickening, structural anomalies, and chromosomal abnormalities were retrospectively analyzed during the quality control period. RESULTS: According to the curve equation of the American NTQR project group, the NT-MoM value before quality control was 0.921 7 MoM, the (SD) log10MoM value was 0.091 92, and the SNC value was 12.20%. After quality control, the NT-MoM value was 0.948 3 MoM, the (SD) log10MoM value was 0.094 81, and the SNC value was 11.43%. The comparison of NT-MoM values before and after quality control showed a statistically significant difference (P<0.000 1). The comparison of NT-MoM values measured by ultrasound physicians with different years of experience before and after quality control also showed statistically significant differences (P<0.000 1). The NT-MoM values for the 3-6 years and >6 years groups were higher after quality control (P<0.05), while the <3 years group showed no significant difference before and after quality control (P>0.05). After quality control, cases of NT thickening without significant structural abnormalities accounted for 19.05%, NT thickening with structural abnormalities accounted for 47.62%, and NT normal with structural abnormalities accounted for 33.33%. There were 36 cases of fetal heart abnormalities, accounting for 20.34% of the total abnormality rate, with a positive rate of 36% in chromosome tests. CONCLUSIONS: After quality control, ultrasound physicians measure NT more accurately, but differences among measurements remain. Measurements by experienced ultrasound physicians are closer to expected values, usually lower than expected. Monitoring fetal NT and CRL measurements helps improve measurement accuracy. Increasing structural screening during NT examinations, especially for the fetal heart, enhances the detection rate of chromosomal abnormalities.

United States' experience in nuchal translucency measurement: variation according to provider characteristics in over five million ultrasound examinations.

OBJECTIVE: The Nuchal Translucency Quality Review (NTQR) program has provided standardized education, credentialing and epidemiological monitoring of nuchal translucency (NT) measurements since 2005. Our aim was to review the effect on NT measurement of provider characteristics since the program's inception. METHODS: We evaluated the distribution of NT measurements performed between January 2005 and December 2019, for each of the three primary performance indicators of NT measurement (NT median multiples of the median (MoM), SD of log10 NT MoM and slope of NT with respect to crown-rump length (CRL)) for all providers within the NTQR program with more than 30 paired NT/CRL results. Provider characteristics explored as potential sources of variability included: number of NT ultrasound examinations performed annually (annual scan volume of the provider), duration of participation in the NTQR program, initial credentialing by an alternative pathway, provider type (physician vs sonographer) and number of NT-credentialed providers within the practice (size of practice). Each of these provider characteristics was evaluated for its effect on NT median MoM and geometric mean of the NT median MoM weighted for the number of ultrasound scans, and multiple regression was performed across all variables to control for potential confounders. RESULTS: Of 5 216 663 NT measurements from 9340 providers at 3319 sites, the majority (75%) of providers had an NT median MoM within the acceptable range of 0.9-1.1 and 85.5% had NT median MoM not statistically significantly outside this range. Provider characteristics associated with measurement within the expected range of performance included higher volume of NT scans performed annually, practice at a site with larger numbers of other NT-credentialed providers, longer duration of participation in the NTQR program and alternative initial credentialing pathway. CONCLUSIONS: Annual scan volume, duration of participation in the NTQR program, alternative initial credentialing pathway and number of other NT-credentialed providers within the practice are all associated with outcome metrics indicating quality of performance. It is critical that providers participate in ongoing quality assessment of NT measurement to maintain consistency and precision. Ongoing assessment programs with continuous feedback and education are necessary to maintain quality care. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Sonologist's characteristics related to a higher quality in fetal nuchal translucency measured in primary antenatal care centers.

OBJECTIVE: To assess the quality of nuchal translucency (NT) measurements in primary care and the sonologist's characteristics related with a higher quality. METHODS: The median NT expressed in multiples of the median (MoM) was calculated for each sonologist of 14 participating antenatal primary care centers of the Catalan Institute of Health. A survey to the sonologists was used to establish variables related to higher-quality measurements. RESULTS: The median NT MoM obtained in 16 448 NT measurements, performed by 102 sonologists, was 0.94 MoM. NT underestimation was observed in 46% of the sonologists. Underestimation were less frequent among professionals who performed more than 230 ultrasounds per year (26% vs 53%;p = .022), those who completed the online Fetal Medicine Foundation (FMF) course (22% vs 54%; p = .021), and those who were subject to periodic audits (24% vs 56%; p = .021). Underestimation rate decreased from 60%, to 33% and 14% with the increase of the years of experience from less than 5 years, to 6 to 15 years and more than 15 years of experience, respectively (p = .029). CONCLUSIONS: Higher-quality measurements were demonstrated in sonologists who performed more ultrasounds per year, those with more years of scanning experience, those who completed the online FMF course, and those periodically audited.

Quality management of nuchal translucency ultrasound measurement in Australia.

BACKGROUND: Nuchal translucency measurement has an established role in first trimester screening. Accurate measurement requires that technical guidelines are followed. Performance can be monitored by auditing the distribution of measurements obtained in a series of cases. AIMS: The primary aim is to develop an accessible, theory-based educational program for individuals whose distribution of measurements at audit falls outside an acceptable range, and assess operator performance following this intervention. MATERIALS AND METHODS: Operators whose nuchal translucency measurement distributions fall outside a normal range (38-65% above the median) were expected to undergo a teleconference tutorial. Accessible from anywhere in Australia, the one hour tutorials were run by a senior sonographer (to explain technical ultrasound aspects) and the audit program manager (to explain the audit process). RESULTS: In 2011, 83 operators attended the teleconference tutorials. Compared to a random comparison group of operators meeting standard in 2011, teleconference tutorial attendees were significantly more likely to: (i) operate in rural or regional, rather than metropolitan, centres (P = 0.001); (ii) be less experienced (P < 0.0005); and (iii) have lower annual scan numbers (P = 0.0012). Improvement in nuchal translucency measurement quality was seen after one audit cycle and was maintained over subsequent years. The mean percentage of the study cohort reaching standard over the five-year audit was 77.8% which was not statistically different from the average for the comparison cohort of all other audited operators (79.3%; P = 0.61). CONCLUSIONS: Teleconference tutorials are a convenient, accessible and effective way to obtain immediate and sustained improvement in operator performance.

The nomogram of prenasal thickness and nasal bone ratio and its relationship with nuchal fold in second-trimester fetal ultrasound.

AIM: We aimed to define the normal values of second-trimester fetal prenasal thickness and nasal bone length ratio (PNT/NBL) in a low-risk Turkish population and investigate the relationship between the increased PNT and nuchal fold (NF). METHOD: We retrospectively reviewed the data of 650 cases considered to be euploid fetuses who presented to our clinic between December 2013 and September 2014 for a second-line ultrasound between 17 and 24 weeks. Their PNT, NBL, NF and biometric (BPD, HC, AC, FL and HL) measurements were recorded. RESULTS: A total of 650 cases considered to be euploid fetuses were included in this study. There was a linear increase in PNT with the gestational weeks (mean value 3.01 at weeks 17-18 and 3.76 at weeks 23-24). The PNT/NB ratio showed a slight decrease in advancing gestational weeks (mean value 0.57 at weeks 17-18 and 0.50 at weeks 23-24). The 95th percentile value of the PNT/NB ratio, independent of the gestational week, was 0.76. The values of both PNT and NF increased with advancing gestational weeks, but there was no statistically linear increase between PNT and NF (R2 : 0.115). CONCLUSION: In this study, we provided a nomogram of the PNT/NB ratio. Both NF thickness and PNT should be dealt with as two separate markers. Although the formation mechanisms are thought to be the same in both of them, a strong linear relationship does not exist between them.

Cut-off value of nuchal translucency as indication for chromosomal microarray analysis.

OBJECTIVES: An association between isolated, increased nuchal translucency thickness (NT) and pathogenic findings on chromosomal microarray analysis (CMA) has been reported. A recent meta-analysis reported that most studies use a NT cut-off value of 3.5 mm. However, considering NT distribution and the commonly accepted 5% false-positive rate in maternal serum screening, NT cut-off levels should be reconsidered. The aim of this study was to assess different NT cut-off levels as indication for CMA and to determine whether CMA should be recommended for mildly increased NT of 3.0-3.4 mm. METHODS: This was a retrospective, multicenter study of singleton pregnancies with CMA results and either normal NT and no other finding or with increased NT as the only medical indication for CMA at the time of an invasive procedure (increased NT was considered an isolated finding in cases of advanced maternal age). Women with normal fetal NT who underwent CMA did so at their own request. A single laboratory performed all genetic analyses. Comparative genomic hybridization microarray analysis or single nucleotide polymorphism array technology was used for CMA. If combined first-trimester screening (NT and biochemistry) indicated increased risk for common aneuploidies, the case was excluded. NT was used to divide cases into three groups (≤ 2.9 mm, 3.0-3.4 mm and ≥ 3.5 mm) and their CMA results were compared. RESULTS: CMA results were recorded in 1588 pregnancies, among which 770 fetuses had either normal NT with no other finding or isolated increased NT. Of these, 462 had NT ≤ 2.9 mm, 170 had NT of 3.0-3.4 mm and 138 had NT ≥ 3.5 mm. Pathogenic copy number variants were found in 1.7%, 6.5% and 13.8% of cases, respectively. CONCLUSION: Our results suggest that CMA should be recommended when fetuses have isolated, mildly increased NT (3.0-3.4 mm). Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Quality Requirements for the early Fetal Ultrasound Assessment at 11-13+6 Weeks of Gestation (DEGUM Levels II and III).

The early fetal ultrasound assessment at 11 - 13(+6) weeks of gestation remains the cornerstone of care despite the progress in diagnosing fetal chromosomal defects using cell-free fetal DNA (cffDNA) from the maternal circulation. The measurement of nuchal translucency (NT) allows the risk calculation for the fetal trisomies 21, 18 and 13 but also gives information on those fetal chromosomal defects which are at present unable to be detected using cffDNA. Nuchal translucency is the only auditable parameter at 11 - 13(+6) weeks and gives thus information on the quality of the first trimester anomaly scan. In addition it gives indirect information on the risks for fetal defects and for cardiac anomalies. Also the chances for a healthy live baby can be estimated. As experience with first trimester anomaly scanning increases, and the resolution of the ultrasound equipment has increased substantially, more and more details of the fetal anatomy become accessible at the first trimester scan. Therefore fetal anatomical defects and complex anomalies have become amenable to examination in the first trimester. This guideline describes compulsory and optional parameters for investigation at the first trimester scan and outlines a structured method of examining a first trimester fetus at 11 - 13(+6) weeks of gestation.

Impact of Including or Removing Nuchal Translucency Measurement on the Detection and False-Positive Rates of First-Trimester Down Syndrome Screening.

INTRODUCTION: First-trimester Down syndrome (DS) screening combining maternal age, serum markers (pregnancy-associated plasma protein-A and beta-human chorionic gonadotropin) and nuchal translucency (NT) gives an 85% detection rate for a 5% false-positive rate. These results largely depend on quality assessment of biochemical markers and of NT. In routine practice, despite an ultrasound quality control organization, NT images can be considered inadequate. The aim of the study was to evaluate the consequences for risk calculation when NT measurement is not taken into account. MATERIAL AND METHOD: Comparison of detection and false-positive rates of first-trimester DS screening (PerkinElmer, Turku, Finland), with and without NT, based on a retrospective study of 117,126 patients including 274 trisomy 21-affected fetuses. NT was measured by more than 3,000 certified sonographers. RESULTS: There was no significant difference in detection rates between the two strategies including or excluding NT measurement (86.7 vs. 81.8%). However, there was a significant difference in the false-positive rates (2.23 vs. 9.97%, p < 0.001). DISCUSSION: Sonographers should be aware that removing NT from combined first-trimester screening would result in a 5-fold increase in false-positive rate to maintain the expected detection rates. This should be an incentive for maintaining quality in NT measurement.

Nuchal Translucency Quality Review (NTQR) program: first one and half million results.

OBJECTIVE: To evaluate the performance of first-trimester nuchal translucency (NT) measurement by providers (physician-sonologists and sonographers) within the Nuchal Translucency Quality Review (NTQR) program. METHODS: After training and credentialing providers, the NTQR monitored performance of NT measurement by the extent to which an individual's median multiple of the normal median (MoM) for crown-rump length (CRL) was within the range 0.9-1.1 MoM of a published normal median curve. The SD of log10 MoM and regression slope of NT on CRL were also evaluated. We report the distribution between providers of these performance indicators and evaluate potential sources of variation. RESULTS: Among the first 1.5 million scans in the NTQR program, performed between 2005 and 2011, there were 1 485 944 with CRL in the range 41-84 mm, from 4710 providers at 2150 ultrasound units. Among the 3463 providers with at least 30 scans in total, the median of the providers' median NT-MoMs was 0.913. Only 1901 (55%) had a median NT-MoM within the expected range; there were 89 above 1.1 MoM, 1046 at 0.8-0.9 MoM, 344 at 0.7-0.8 MoM and 83 below 0.7 MoM. There was a small increase in the median NT-MoM according to providers' length of time in the NTQR program and number of scans entered annually. On average, physician-sonologists had a higher median NT-MoM than did sonographers, as did those already credentialed before joining the program. The median provider SD was 0.093 and the median slope was 13.5%. SD correlated negatively with the median NT-MoM (r = -0.34) and positively with the slope (r = 0.22). CONCLUSION: Even with extensive training, credentialing and monitoring, there remains considerable variability between NT providers. There was a general tendency towards under-measurement of NT compared with expected values, although more experienced providers had performance closer to that expected.

Quality of first-trimester measurement of crown-rump length.

OBJECTIVE: The purpose of this study was to evaluate the quality of crown-rump length (CRL) measurements in scans judged to be of high quality for the measurement of the nuchal translucency. STUDY DESIGN: We analyzed prospective data on 68,250 scans by 1913 sonographers that were collected by the French College of Fetal Echography (CFEF) national practice assessment program for the first-trimester scan. The scans were evaluated according to the CFEF image scoring method (CFEF-ISM), which includes items to measure the quality of the scan for both nuchal translucency and the CRL measurements. The scans were classified into 4 quality groups with the use of the full CFEF-ISM score and then a shortened version of the CFEF-ISM that excluded the item on quality of CRL measurement. The proportion of scans with an inaccurate CRL measurement was compared across the different quality groups. RESULTS: Overall, 21.67% of scans were of insufficient quality for CRL measurement. Among 23,764 "excellent" scans according to the full CFEF-ISM, 965 scans (4.06%) had insufficient CRL quality vs 9.24% of scans with "excellent" quality on the short CFEF-ISM (relative risk, 2.27; 95% confidence interval, 2.11-2.44; P < .001). CONCLUSION: High scores of the quality of nuchal translucency measurement do not guarantee accurate measurement of crown-rump length. Specific measures are needed to evaluate and to improve the quality of the measurement of crown-lump length.

Accuracy of nuchal translucency measurement depends on equipment used and its calibration.

OBJECTIVES: To determine the effect of different ultrasound machine-probe combinations on nuchal translucency (NT) measurements and to assess how this impacts on the accuracy of the NT-derived component of first-trimester screening for trisomy 21. METHODS: Sixteen different ultrasound machine-probe combinations were used for axial measurement of 2.0-, 3.0- and 4.0-mm spaced targets in an ultrasound phantom. Differences between the measured and known values were determined. The mean of the axial measurements was used to calculate adjusted risks for trisomy 21, given specific clinical scenarios. RESULTS: Differences observed using different machine-probe combinations for the 2.0-mm target ranged from 1.8-2.2 mm; for the 3.0-mm target, 2.7-3.2 mm; and for the 4-mm target, 3.7-4.3 mm, and exceeded those due to intraobserver variability. For a fetal crown-rump length of 50.0 mm and NT measurement of 2.0 mm, the maximum/minimum measurements in the fetus of a 40-year-old woman led to derived risks ranging from 1 in 32 (NT, 2.2 mm) to 1 in 189 (NT, 1.8 mm) and in the fetus of a 20-year-old with an NT of 3.0 mm these ranged from 1 in 102 (NT, 3.2 mm) to 1 in 160 (NT, 2.7 mm). CONCLUSIONS: We have described the effect of machine-probe combinations on small but very precise ultrasound measurements. Such machine-probe combinations led to greater variability than those ascribed to intraobserver differences, and significantly affected the screening risk for the same fixed measurement. This finding has implications for Down syndrome screening algorithms and audit of ultrasound operators. Furthermore, most ultrasound machines are neither calibrated nor specified for measurements of tenths of a mm.

Exponentially weighted moving average chart as a suitable tool for nuchal translucency quality review.

OBJECTIVES: This study aimed to design an exponentially weighted moving average (EWMA) chart for the quality review of nuchal translucency (NT) and to assess its performance compared with the methods currently in use: retrospective distribution-based methods and the cumulative sum (CUSUM) chart. METHODS: The EWMA model was designed for NT quality review using simulation. The NT measurements obtained during routine first-trimester screening in our centre over a two-and-a-half-year period were retrieved from the database. The NT distribution parameters, EWMA and CUSUM chart were established, and the methods were compared. RESULTS: On the basis of the results from the simulation, the optimal EWMA settings were established. A set of 9338 NT measurements obtained from nine sonographers was used to construct the EWMA and CUSUM charts and to calculate the distribution parameters. Distribution-based methods were unable to reveal the temporal periods of poor performance. The EWMA model agreed closely with the CUSUM but had the advantage promptly indicating when the process returned to an in-control state, thus extending its use to long-term prospective and retrospective quality assessments. CONCLUSIONS: The EWMA provides a universal, easy and efficient tool for NT quality review when the prompt and effective detection of suboptimal performance is desired.

Do clinical practitioners seeking credentialing for nuchal translucency measurement demonstrate compliance with biosafety recommendations? Experience of the Nuchal Translucency Quality Review Program.

OBJECTIVES: The purpose of this study was to evaluate compliance with the ALARA (as low as reasonably achievable) principle by practitioners seeking credentialing for nuchal translucency (NT) measurement between 11 and 14 weeks' gestation. METHODS: Nuchal Translucency Quality Review Program credentialing requires quantitative scoring of 5 NT measurements from 5 different fetuses. Images submitted by 100 consecutive practitioners were retrospectively evaluated for the output display standard (ODS). The thermal index (TI) type (bone [TIb] or soft tissue [TIs]) and numeric value of the index were recorded. The TIb was considered the correct index for this study. Compliance with the numeric value was evaluated in several ways. Collectively, a TIb lower than 0.5 was considered optimal, lower than 0.7 compliant, and 1.0 or lower satisfactory. RESULTS: An ODS was present in at least 1 image submitted by 77 practitioners. The TIb was used exclusively by 15 (19.5%), the TIs by 37 (48.1%), and 25 used a combination of the TIb and TIs. Only 4 of 77 providers (5%) used the correct TI type (TIb) at lower than 0.5 for all submitted images, 5 of 77 (6%) at lower than 0.7, and 9 of 77 (12%) at 1.0 or lower. A TI (TIb or TIs) higher than 1.0 was used by 15 of 77 providers (19.5%). Proficiency in NT measurement and educational background (physician or sonographer) did not influence compliance with ALARA. CONCLUSIONS: Clinicians seeking credentialing in NT do not demonstrate compliance with the recommended use of the TIb in monitoring acoustic output.

Impact of gestational age on nuchal fold thickness in the second trimester.

OBJECTIVES: The purpose of this study was to establish gestational age (GA)-specific nomograms for nuchal fold thickness between 16 and 24 weeks. METHODS: This retrospective cross sectional study included 32,207 women who underwent a second-trimester anomaly scan at the Fetal Care Center of National University Hospital from January 2005 to April 2011. Nomograms were plotted for nuchal fold thickness at each gestation to study its variation with GA. RESULTS: Nuchal fold thickness increased with GA in a linear manner from 3.13 ± 0.68 mm (mean ± SD) at 16 weeks to 5.08 ± 0.76 mm at 24 weeks. The 95th percentile measurement at 24 weeks remained less than 6 mm. CONCLUSIONS: A threshold of 6 mm appears to be appropriate for the diagnosis of a thick nuchal fold even for gestations between 20 and 24 weeks.

Nuchal translucency measurement: are qualitative and quantitative quality control processes related?

OBJECTIVES: Two types of quality assurance processes for nuchal translucency (NT) measurement have been described: qualitative through review of images and quantitative comparison of operator's specific NT distribution to reference distributions. The aim of this study was to assess the results of these two approaches. METHODS: Prospective evaluation of sonologists affiliated to the French Ultrasound College who first underwent qualitative evaluation based on the College Français d'Echographie Foetale (CFEF) score. During one year, those same sonologists measured the NT for Down syndrome screening purposes. The operator's specific NT distributions were compared to their CFEF score, their number of unsatisfactory images and their number of NT measurements per year. RESULTS: The study involved 1726 sonologists who performed 174 722 first-trimester examinations. Mean (SD) quantitative score was 23.4/32 (+/-7.4). The median [inter-quantile range] number of examinations per sonologist was 69 [37; 123]. The median [range] NT multiples of the mean (MoM) value was 0.81 [0.46; 1.22]. NT (MoM) absolute deviation from 1 MoM was significantly correlated with mean score obtained (R(2) = -0.17, p < 0.0001), number of unacceptable images (R(2) = 0.14, p < 0.0001) and number of ultrasound scans performed per year (R(2) = -0.19, p < 0.0001). CONCLUSION: Our results suggest that both processes are clearly related.

Intra-operator and inter-operator reliability of manual and semiautomated measurement of fetal nuchal translucency: a cross sectional study.

OBJECTIVE: The goal of this study was to examine the intra-operator and inter-operator differences of the manual and semiautomated nuchal translucency (NT) measurements and to evaluate if these differences alter women's risk status. METHODS: A cross sectional study was performed. Two operators obtained manual and semiautomated NT measurements of 153 NT images. The maximal acceptable difference in NT measurements within and between operators was 0.15 mm. Intra and inter-operator differences were analyzed by the paired Student's t-test and homogeneity of variances by the Levene's test. Intra-operator and inter-operator agreement were quantified with Bland and Altman's limits of agreement, and changes in women's risk status were tested with the binomial test. RESULTS: Intra-operator agreement was high for each of the measurement methods. Operator 1 had lower SDS for manual measurements. Conversely, operator 2 had lower SDS of the differences for semiautomated measurements, although the SD never reached the same level as operator 1. Inter-operator agreement was highest for the semiautomated measurements. Changes in risk status occurred between the manual and inner-middle method resulting in different clinical policies in up to 1 out of 20 cases. CONCLUSION: Well-trained operators do not seem to benefit from the use of the semiautomated measurement methods.

Evaluation of the fetal heart at 14 to 18 weeks' gestation in fetuses with a screening nuchal translucency greater than or equal to the 95th percentile.

OBJECTIVES: The purpose of this study was to determine whether normal fetal cardiac anatomy could be successfully demonstrated and congenital heart disease detected transabdominally at 14 to 18 weeks' gestation in fetuses with a nuchal translucency greater than or equal to the 95th percentile. METHODS: In this retrospective chart review, grayscale images, Z scores, and Doppler evaluations, including pulsed, color, and spectral Doppler imaging, were reviewed to determine whether fetal heart evaluation findings at 14 to 18 weeks' gestation were normal or abnormal. RESULTS: Normal cardiac anatomy was successfully evaluated in 32 of 33 normal cases; only an aortic arch and a ductal arch were not successfully visualized in 1 case. Major congenital heart disease was detected prenatally in 4 abnormal cases. CONCLUSIONS: The fetal heart can be successfully evaluated at an earlier gestational age but may be dependent on the skill of the sonographer and reading physician. Maternal decisions can be made earlier in gestation, before the pregnancy is obvious, and can allow planning for a pregnancy that will need to be delivered at a medical center that has a level 3 nursery.

An audit of first trimester ultrasound screening for chromosomal abnormalities.

BACKGROUND: Screening for Down syndrome has been funded in New Zealand since 2010 following the report 'Antenatal Down Syndrome Screening in NZ 2007' which identified that the practice of screening using maternal age and/or nuchal translucency (NT) without biochemical markers was unsafe and should not continue. AIM: This study aimed to assess the quality of the ultrasound component of first trimester screening in a metropolitan population. METHODS: Over a 5-month period, all available NT scan images for women referred to the Central Region Fetal Medicine Unit for an increased risk at first trimester screening or a fetal abnormality detected at the 20-week ultrasound scan were reviewed according to the Fetal Medicine Foundation (FMF) criteria and utilising the Herman Score. This is the standard which the National Screening Unit (NSU) and Ministry of Health (MOH) have mandated for the ultrasound component of the screening test. RESULTS: Of the 52 images, 4 (7.7%) studies were considered unacceptable and another 5 (9.6%) were considered intermediate. The mean score was 5.87 of a possible score of 9. Comparisons with Herman's data are presented and discussed. CONCLUSIONS: This review suggests that there is potential for the quality of the ultrasound component of the first trimester screening component to improve. This would in turn improve the performance of the screening program. We conclude that formal quality control of this screening program is urgently required.

Improvement of a prenatal screening program for trisomy 18 in the first trimester of gestation.

BACKGROUND: The aim of this study was to evaluate population parameters (medians, standard deviations and coefficients of correlation) different from those used by the commercial software Elipse(®) v3.0 (Perkin Elmer) in the calculation of prenatal risk of trisomy 18. Moreover, the truncation limits used for extreme values of free ß-human chorionic gonadotropin (fß-hCG), pregnancy associated plasma protein-A (PAPP-A) and nuchal translucency (NT) were revised. METHODS: A calculation engine for the prenatal risk of trisomy 18 was developed [called FMF (Fetal Medicine Foundation) calculator]. Recently, published population parameters for fß-hCG and PAPP-A as well as new truncation limits were included in this calculator. The patient-specific risks obtained by Elipse(®) v3.0 and FMF calculators, were compared in 18,801 pregnant women, including 13 cases of trisomy 18, four cases of trisomy 13 and one case of triploidy. RESULTS: Using a cut-off point of 1:250, FMF calculator increased the detection rate of trisomy 18 from 62% to 100% with a 0.31% increase in the false-positive rate (FPR). When the detection rate was fixed at 100%, the FPR generated by Elipse v3.0 (1.52%) was significantly higher (p<0.0001) than that generated by the FMF calculator (0.36%). Moreover, an improved detection in cases of trisomy 13 and triploidy was observed. CONCLUSIONS: It is recommended that each laboratory reviews the population parameters and truncation limits used in the risk calculation of trisomy 18, in order to obtain an adequate performance in the screening.